The present invention relates to power steering means of vehicles and more particularly to a method and system for controlling a power steering device of electrically-driven type of a vehicle.
As is known, a power steering device of a vehicle which is steered by turning a steering wheel operates in accordance with the torque transmitted through the steering shaft to generate assist power for steering manipulation. In the known power steering devices the most widely used are those of the oil pressure (hydraulic) type (as described, for example, in Japanese Utility Model Laid-Open Publn. No. 44181/1978) and those of the electrically-driven type (as described, for example, in Japanese Patent Laid-Open Publn. No. 1808/1974).
In a steering system provided with a power steering device as mentioned above, the power steering device generates an excessively large assist torque in dependence on the excessive steering torque and is subjected to larger load than necessary. This is carried out in the case where the steering wheel is turned fully in one direction to strike against a stop mechanism and thereafter is held in place by the application thereto of additional force.